Telecommunications apparatus and methods

ABSTRACT

A method of operating a terminal device capable of coverage enhancement in a wireless telecommunication system including receiving a signal from a base station within the wireless telecommunication system, measuring the received signal strength of the received signal, comparing the measured signal strength with at least one threshold value, and selecting a mode of operation of coverage enhancement based on a result of the comparison.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/548,429, filed Aug. 3, 2017, which is based on PCT filingPCT/EP2015/080811, filed Dec. 21, 2015, which claims priority to EP15154857.5, filed Feb. 12, 2015, the entire contents of each areincorporated herein by reference.

BACKGROUND Field

The present disclosure relates to telecommunications apparatus andmethods.

Description of Related Art

The “background” description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent it is described in thisbackground section, as well as aspects of the description which may nototherwise qualify as prior art at the time of filing, are neitherexpressly or impliedly admitted as prior art against the presentinvention.

The present disclosure relates to wireless telecommunications systemsand methods.

Mobile communication systems have evolved over the past ten years or sofrom the GSM System (Global System for Mobile communications) to the 3Gsystem and now include packet data communications as well as circuitswitched communications. The third generation partnership project (3GPP)is developing a fourth generation mobile communication system referredto as Long Term Evolution (LTE) in which a core network part has beenevolved to form a more simplified architecture based on a merging ofcomponents of earlier mobile radio network architectures and a radioaccess interface which is based on Orthogonal Frequency DivisionMultiplexing (OFDM) on the downlink and Single Carrier FrequencyDivision Multiple Access (SC-FDMA) on the uplink.

Third and fourth generation mobile telecommunication systems, such asthose based on the 3GPP defined UMTS and Long Term Evolution (LTE)architectures, are able to support a more sophisticated range ofservices than simple voice and messaging services offered by previousgenerations of mobile telecommunication systems.

For example, with the improved radio interface and enhanced data ratesprovided by LTE systems, a user is able to enjoy high data rateapplications such as mobile video streaming and mobile videoconferencing that would previously only have been available via a fixedline data connection. The demand to deploy third and fourth generationnetworks is therefore strong and the coverage area of these networks,i.e. geographic locations where access to the networks is possible, isexpected to increase rapidly.

The anticipated widespread deployment of third and fourth generationnetworks has led to the parallel development of a class of devices andapplications which, rather than taking advantage of the high data ratesavailable, instead take advantage of the robust radio interface andincreasing ubiquity of the coverage area. Examples include so-calledmachine type communication (MTC) applications, some of which are in somerespects typified by semi-autonomous or autonomous wirelesscommunication devices (MTC devices) communicating small amounts of dataon a relatively infrequent basis. Examples include so-called smartmeters which, for example, are located in a customer's home andperiodically transmit data back to a central MTC server relating to thecustomer's consumption of a utility such as gas, water, electricity andso on. Smart metering is merely one example of potential MTC deviceapplications. Further information on characteristics of MTC-type devicescan be found, for example, in the corresponding standards, such as ETSITS 122 368 V11.6.0 (2012 September)/3GPP TS 22.368 version 11.6.0Release 11) [1].

Whilst it can be convenient for a terminal such as an MTC-type terminalto take advantage of the wide coverage area provided by a third orfourth generation mobile telecommunication network there are at presentdisadvantages. Unlike a conventional third or fourth generation mobileterminal such as a smartphone, a primary driver for MTC-type terminalswill be a desire for such terminals to be relatively simple andinexpensive. The type of functions typically performed by an MTC-typeterminal (e.g. simple collection and reporting/reception of relativelysmall amounts of data) do not require particularly complex processing toperform, for example, compared to a smartphone supporting videostreaming. However, third and fourth generation mobile telecommunicationnetworks typically employ advanced data modulation techniques andsupport wide bandwidth usage on the radio interface which can requiremore complex and expensive radio transceivers and decoders to implement.It is usually justified to include such complex elements in a smartphoneas a smartphone will typically require a powerful processor to performtypical smartphone type functions. However, as indicated above, there isnow a desire to use relatively inexpensive and less complex deviceswhich are nonetheless able to communicate using LTE-type networks.

With this in mind there has been proposed a concept of so-called“virtual carriers” operating within the bandwidth of a “host carrier”,for example, as described in GB 2 487 906 [2], GB 2 487 908 [3], GB 2487 780 [4], GB 2 488 513 [5], GB 2 487 757 [6], GB 2 487 909 [7], GB 2487 907 [8] and GB 2 487 782 [9]. One principle underlying the conceptof a virtual carrier is that a frequency subregion (subset of frequencyresources) within a wider bandwidth (greater range of frequencyresources) host carrier is configured for use as a self-containedcarrier for at least some types of communications with certain types ofterminal device.

In some implementations, such as described in references [2] to [9], alldownlink control signalling and user-plane data for terminal devicesusing the virtual carrier are conveyed within the subset of frequencyresources associated with the virtual carrier. A terminal deviceoperating on the virtual carrier is made aware of the restrictedfrequency resources and need only receive and decode a correspondingsubset of transmission resources to receive data from the base station.An advantage of this approach is to provide a carrier for use bylow-capability terminal devices capable of operating over onlyrelatively narrow bandwidths. This allows devices to communicate onLTE-type networks, without requiring the devices to support fullbandwidth operation. By reducing the bandwidth of the signal that needsto be decoded, the front end processing requirements (e.g., FFT, channelestimation, subframe buffering etc.) of a device configured to operateon a virtual carrier are reduced since the complexity of these functionsis generally related to the bandwidth of the signal received.

Other virtual carrier approaches for reducing the required complexity ofdevices configured to communicate over LTE-type networks are proposed inGB 2 497 743 [10] and GB 2 497 742 [11]. These documents propose schemesfor communicating data between a base station and a reduced-capabilityterminal device whereby physical-layer control information for thereduced-capability terminal device is transmitted from the base stationusing subcarriers selected from across a full host carrier frequencyband (as for conventional LTE terminal devices). However, higher-layerdata for reduced-capability terminal devices (e.g. user-plane data) istransmitted using only subcarriers selected from within a restrictedsubset of carriers which is smaller than and within the set ofsubcarriers comprising the system frequency band. Thus, this is anapproach in which user-plane data for a particular terminal device maybe restricted to a subset of frequency resources (i.e. a virtual carriersupported within the transmission resources of a host carrier), whereascontrol signalling is communicated using the full bandwidth of the hostcarrier. The terminal device is made aware of the restricted frequencyresource, and as such need only buffer and process data within thisfrequency resource during periods when higher-layer data is beingtransmitted. The terminal device buffers and processes the full systemfrequency band during periods when physical-layer control information isbeing transmitted. Thus, the reduced-capability terminal device may beincorporated in a network in which physical-layer control information istransmitted over a wide frequency range, but only needs to havesufficient memory and processing capacity to process a smaller range offrequency resources for the higher-layer data. This approach maysometimes be referred to as a “T-shaped” allocation because the area ofthe downlink time-frequency resource grid to be used by thereduced-capability terminal device may in some cases comprise agenerally T-shape.

Virtual carrier concepts thus allow terminal devices having reducedcapabilities, for example in terms of their transceiver bandwidth and/orprocessing power, to be supported within LTE-type networks. As notedabove, this can be useful for to allow relatively inexpensive and lowcomplexity devices to communicate using LTE-type networks. However,providing support for reduced capability devices in a wirelesstelecommunications system which is generally based around existingstandards can require additional considerations for some operationalaspects of wireless telecommunications systems to allow thereduced-capability terminal devices to operate in conjunction withconventional terminal devices.

One area where the inventors have recognised a need for new proceduresconcerns the acquisition of system information. In broad summary, systeminformation, or at least some aspects of system information, in existingwireless telecommunications systems, such as LTE-basedtelecommunications systems, is transmitted for all terminal devices in abroadcast manner. This system information is transmitted in blocks ofdata called Master Information Blocks (MIBs) and System InformationBlocks (SIBs). In the context of coverage enhancement, it is sometimesdifficult for a terminal device (whether reduced capability or not) toreceive large MIBs and SIBs. There is therefore a need for schemes whichallows system information to be communicated to terminal devicesoperating in a coverage enhancement situation.

SUMMARY

According to one embodiment, there is provided a method of operating aterminal device capable of coverage enhancement in a wirelesstelecommunication system comprising receiving a signal from a basestation within the wireless telecommunication system, measuring thereceived signal strength of the received signal, comparing the measuredsignal strength with at least one threshold value and selecting the modeof operation of coverage enhancement based on the result of thecomparison.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings wherein likereference numerals designate identical or corresponding parts throughoutthe several views, and wherein:

FIG. 1 schematically represents an example of a LTE-type wirelesstelecommunication network;

FIG. 2 schematically represents some aspects of a LTE downlink radioframe structure;

FIG. 3 schematically represents some aspects of a LTE downlink radiosubframe structure;

FIG. 4 schematically represents some aspects of a LTE downlink radiosubframe structure associated with a host carrier supporting a virtualcarrier;

FIG. 5 schematically represents some aspects of a series of radiosubframes spanning a system information modification period boundary fora host carrier supporting a virtual carrier;

FIG. 6 schematically represents a block of system information containingscheduling information along with a block of system informationcontaining scheduling information according to an example of the presentdisclosure;

FIG. 7 shows a timing diagram for the blocks of system informationaccording to FIG. 6;

FIG. 8 shows a timing diagram for an example MTC device receiving theblock of FIG. 6;

FIG. 9 shows a flow diagram explaining the process according to thepresent disclosure; and

FIG. 10 schematically represents an adapted LTE-type wirelesstelecommunications system arranged in accordance with an example of thepresent disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 provides a schematic diagram illustrating some basicfunctionality of a wireless telecommunications network/system 100operating in accordance with LTE principles. Various elements of FIG. 1and their respective modes of operation are well-known and defined inthe relevant standards administered by the 3GPP® body and also describedin many books on the subject, for example, Holma, H. and Toskala, A.[12].

The network 100 includes a plurality of base stations 101 connected to acore network 102. Each base station provides a coverage area 103 (i.e. acell) within which data can be communicated to and from terminal devices104. Data are transmitted from base stations 101 to terminal devices 104within their respective coverage areas 103 via a radio downlink. Dataare transmitted from terminal devices 104 to the base stations 101 via aradio uplink. The core network 102 routes data to and from the terminaldevices 104 via the respective base stations 101 and provides functionssuch as authentication, mobility management, charging and so on.Terminal devices may also be referred to as mobile stations, userequipment (UE), user terminal, mobile radio, and so forth. Base stationsmay also be referred to as transceiver stations/nodeBs/e-NodeBs, and soforth.

Mobile telecommunications systems such as those arranged in accordancewith the 3GPP defined Long Term Evolution (LTE) architecture use anorthogonal frequency division multiplex (OFDM) based interface for theradio downlink (so-called OFDMA) and a single carrier frequency divisionmultiplex based interface for the radio uplink (so-called SC-FDMA). FIG.2 shows a schematic diagram illustrating an OFDM based LTE downlinkradio frame 201. The LTE downlink radio frame is transmitted from an LTEbase station (known as an enhanced Node B) and lasts 10 ms. The downlinkradio frame comprises ten subframes, each subframe lasting 1 ms. Aprimary synchronisation signal (PSS) and a secondary synchronisationsignal (SSS) are transmitted in the first and sixth subframes of the LTEframe. A physical broadcast channel (PBCH) is transmitted in the firstsubframe of the LTE frame.

FIG. 3 is a schematic diagram of a grid which illustrates the structureof an example conventional downlink LTE subframe (corresponding in thisexample to the first, i.e. left-most, subframe in the frame of FIG. 2).The subframe comprises a predetermined number of symbols which aretransmitted over a 1ms period. Each symbol comprises a predeterminednumber of orthogonal sub-carriers distributed across the bandwidth ofthe downlink radio carrier.

The example subframe shown in FIG. 3 comprises 14 symbols and 1200sub-carriers spread across a 20 MHz bandwidth. The smallest allocationof user data for transmission in LTE is a resource block comprisingtwelve sub-carriers transmitted over one slot (0.5 subframe). Forclarity, in FIG. 3, each individual resource element (a resource elementcomprises a single symbol on a single subcarrier) is not shown, insteadeach individual box in the subframe grid corresponds to twelvesub-carriers transmitted on one symbol.

FIG. 3 shows resource allocations for four LTE terminals 340, 341, 342,343. For example, the resource allocation 342 for a first LTE terminal(UE 1) extends over five blocks of twelve sub-carriers (i.e. 60sub-carriers), the resource allocation 343 for a second LTE terminal(UE2) extends over six blocks of twelve sub-carriers and so on.

Control channel data are transmitted in a control region 300 (indicatedby dotted-shading in FIG. 3) of the subframe comprising the first nsymbols of the subframe where n can vary between one and three symbolsfor channel bandwidths of 3 MHz or greater and where n can vary betweentwo and four symbols for channel bandwidths of 1.4 MHz. For the sake ofproviding a concrete example, the following description relates tocarriers with a channel bandwidth of 3 MHz or greater so the maximumvalue of n will be 3. The data transmitted in the control region 300includes data transmitted on the physical downlink control channel(PDCCH), the physical control format indicator channel (PCFICH) and thephysical HARQ indicator channel (PHICH).

PDCCH contains control data indicating which sub-carriers on whichsymbols of the subframe have been allocated to specific LTE terminals.Thus, the PDCCH data transmitted in the control region 300 of thesubframe shown in FIG. 3 would indicate that UE1 has been allocated theblock of resources identified by reference numeral 342, that UE2 hasbeen allocated the block of resources identified by reference numeral343, and so on.

PCFICH contains control data indicating the size of the control region(i.e. between one and three symbols).

PHICH contains HARQ (Hybrid Automatic Request) data indicating whetheror not previously transmitted uplink data has been successfully receivedby the network.

Symbols in a central band 310 of the time-frequency resource grid areused for the transmission of information including the primarysynchronisation signal (PSS), the secondary synchronisation signal (SSS)and the physical broadcast channel (PBCH). This central band 310 istypically 72 sub-carriers wide (corresponding to a transmissionbandwidth of 1.08 MHz). The PSS and SSS are synchronisation signals thatonce detected allow an LTE terminal device to achieve framesynchronisation and determine the cell identity of the enhanced Node Btransmitting the downlink signal. The PBCH carries information about thecell, comprising a master information block (MIB) that includesparameters that LTE terminals use to properly access the cell. Datatransmitted to individual LTE terminals on the physical downlink sharedchannel (PDSCH) can be transmitted in other resource elements of thesubframe.

FIG. 3 also shows a region of PDSCH containing system information andextending over a bandwidth of R344.

A conventional LTE frame will also include reference signals which arenot shown in FIG. 3 in the interests of clarity.

FIG. 4 is a diagram which is similar to and will in many respect beunderstood from FIG. 3. However, FIG. 4 differs from FIG. 3 inschematically representing a downlink radio subframe corresponding to ahost carrier in which a virtual carrier 401 (VC) is supported. Thegeneral operation of the virtual carrier represented in FIG. 4 may be inaccordance with previously-proposed schemes, for example as described inany of the above-identified documents [2] to [11]. The virtual carrierthus represents a restricted subset of downlink transmission resourceswithin the overall transmission resource grid associated with the hostcarrier which may be used for communicating at least some informationwith certain types of terminal devices, for example, reduced capabilitymachine type communication terminal devices.

Thus, a conventional (i.e. non-reduced capability) terminal device maybe supported using the full bandwidth of the resource grid representedin FIG. 4 in accordance with conventional LTE techniques. Downlinkcommunications for a reduced-capability terminal device, on the otherhand, may be restricted to a subset of transmission resources within thevirtual carrier.

In some cases the entirety of the downlink communications for thereduced-capability terminal device (i.e. including control signallingand higher layer/user-plane data) may be conveyed within thetransmission resources of one of the virtual carriers, for example inaccordance with the principles proposed in the above-identifieddocuments [2] to [9]. This may be appropriate, for example, for aterminal device which cannot receive the full bandwidth of the hostcarrier (and hence cannot receive the entirety of the control region300).

In other cases the reduced-capability terminal device may be able toreceive the full-bandwidth of the host carrier (and hence receive anddecode the control region 300), but may be restricted as to its abilityto buffer and decodes the entirety of the PDSCH region, and so maybuffer and decode only a subset of the downlink transmission resourcesspanning the virtual carrier to which the terminal device has beenallocated, for example in accordance with the “T-shaped allocation”principles proposed in the above-identified documents [10] and [11].While this mode of operation may be referred to as a “T-shapedallocation” mode of operation for ease of reference, the PDSCH resourcesallocated to the reduced-capability terminal device need not becontiguous in frequency. That is to say that while the virtual carrierresources schematically represented in FIG. 4 are shown as a continuousblock, in some examples the restricted subset of resources may be asubset of OFDM carriers distributed (spread) across the systembandwidth. Furthermore, it will be appreciated the subset of OFDMsubcarriers comprising a virtual carrier for one particular terminaldevice may be different from a subset of OFDM subcarriers associatedwith supporting virtual carrier operation for another terminal device.

As noted above, virtual carrier operation can have an impact on howsystem information changes can be received by a reduced-capabilityterminal device.

In an LTE-based wireless telecommunications system some of thefundamental information required for a terminal device to operate in acell is transmitted on PBCH in the Master Information Block (MIB). Otherinformation regarding the system configuration is divided among SystemInformation Blocks (SIBs) referred to as SIB1, SIB2, SIB3, . . . etc.(there are 16 SIBs defined as of Release 11 LTE). The SIBs aretransmitted in system information (SI) messages, which, apart from SIB1,may contain multiple SIBs. There may be one or several SI messagestransmitted at different periodicities. Each SI message may conveymultiple SIBs suitable for scheduling with the same periodicity. Thetimings for SIB1 transmissions are fixed on an 80 ms period and theyoccur in the fifth subframe of radio frames when System Frame Number(SFN) is a multiple of 8 (i.e. SFN mod 8=0). There are retransmissionsof SIB1 provided in every other radio frame within the 80 ms period. Thetimings for other SIB transmissions are configured in SIB1. Thetransmission resource allocations for the SI messages on PDSCH within asubframe are provided to terminal devices using PDCCH allocationmessages addressed to SI-RNTI (System Information Radio NetworkTemporary Identifier—currently 0xFFFF in LTE). At higher layers, SI iscarried on the logical broadcast control channel (BCCH).

The system information in a cell may be changed, although typically thishappens rarely with system information perhaps remaining unchanged forhours, days, or even weeks.

For changes of system information other than those related to EAB(Extended Access Barring), ETWS (Earthquake Tsunami Warning System) andCMAS (Commercial Mobile Alert System), there is a BCCH modificationperiod defined (which may be referred to as a “SI modification period”).SI modification period boundaries are defined on radio frames for whichSFN mod q=0, for a cell-specific value of q. When there is a change insystem information, the new system information is transmitted from thestart of a new SI modification period.

The general process for implementing scheduling in system information inan LTE-based network is described, for example, in Section 5.2.1.2 ofETSI TS 136 331 V11.4.0 (2013 July)/3GPP TS 36.331 version 11.4.0Release 11 [13]. In summary, a base station indicates a change of systeminformation as follows.

More details on system information and scheduling in system informationin an LTE-based system can be found in ETSI TS 136 331 V11.4.0 (2013July)/3GPP TS 36.331 version 11.4.0 Release 11 [13].

As discussed above, it has been proposed to reduce the complexity of anLTE modem by reducing the baseband bandwidth over which certain types ofterminal device operate. In particular, it may be desirable to reduce atleast the baseband bandwidth over which the terminal device is toreceive PDSCH (i.e. using T-shaped allocation virtual carriertechniques). This can have the advantages of lowering the complexity ofsubframe buffering, post-FFT buffering, channel estimation, and turbodecoding; and lower complexity creates an opportunity for lower modemcost and also reduced operational power consumption. Low complexitymodems are particularly attractive for use in machine-type communication(MTC) terminal devices.

Such a reduced-capability terminal device might, for example, be adaptedto receive PDCCH across a full system bandwidth spanning n physicalresource blocks (PRBs), e.g. n=50 PRBs for a system bandwidth of 10 MHzat baseband. However, the terminal device might be adapted to receivePDSCH in a maximum of m PRBs, where m is less than n. For example m=6,corresponding to an effective bandwidth of 1.4 MHz at baseband forPDSCH.

The buffering requirements can be reduced if the UE is given anindication of which m PDSCH PRBs it must buffer before it needs todecode them, so that a buffer suitable for 6 instead of 50 PRBs can beprovided. Since the RF bandwidth is not changed, these 6 PDSCH PRBscould be anywhere within the system bandwidth and, in general, might becontiguous or non-contiguous in frequency per subframe. In the subframein which PDSCH decoding occurs, PDCCH can schedule any subset or thewhole of the 6 PRBs since all 6 have been buffered by the UE. Someexample techniques for establishing the predetermined subset of PDSCHresources to buffer at the terminal device can be found in GB 2 497 743[10] and GB 2 497 742 [11], but in general any suitable technique can beused.

The restricted subset of transmission resources on which areduced-capability terminal device can receive PDSCH in a given subframeimpacts how system information messages should be handled in thewireless telecommunications system. A PDCCH resource allocation toSI-RNTI to indicate a change in system information is transmitted in thePDCCH common search space, and therefore all terminal devices receivethe relevant SIBs using the same PDSCH resources (at least for systeminformation which is relevant for all terminal devices). To bereceivable by a reduced-capability terminal device, the SIBs should bescheduled on physical resource blocks which the reduced-capabilityterminal device will buffer in the relevant subframe. Furthermore, thiswill be a restricted number of PRBs, e.g. requiring SIBs to betransmitted within m (e.g. m=6) PRBs.

However, the base station also needs send user data to reducedcapability (low complexity) terminal devices using the restricted subsetof PDSCH resources for the terminal device. To help increase the numberof reduced-capability terminal devices that can be supported in anetwork and overall scheduling flexibility, it can be helpful ifdifferent reduced-capability terminal devices can operate usingdifferent restricted subsets of transmission resources. This means thePDSCH resource blocks which different terminal devices are buffering toreceive their own user data will not in general be the same resourceblocks in which system information (SIBs) is sent. The previouslyproposed schemes for virtual carrier operation have addressed how aterminal device can acquire system information when attaching to anetwork, notwithstanding the terminal device's ability to decode only arestricted subset of PDSCH resources in a given subframe. However,different techniques may be needed when a reduced-capability terminaldevice is to acquire new system information, for example because of achange in system information, while it is connected to the network (e.g.in RRC connected mode).

FIG. 5 schematically represents a downlink frequency resource gridspanning four subframes labelled as SFn, SFn+1, SFn+2 and SFn+3 for anLTE-based wireless telecommunications system supporting a virtualcarrier mode of operation in which a reduced-capability terminal deviceis restricted to buffering a subset of PDSCH resources while being ableto receive the full bandwidth of PDCCH resources. As described above,each subframe comprises a PDCCH region 560 and a PDSCH region 562.Subframes SFn+1 and SFn+2 are assumed to span a system informationmodification period boundary 564, as schematically represented in thefigure. Schematically represented in the PDSCH region of each subframeis an indication of the subset of transmission resources 566 which anexample reduced-capability terminal device would use if it werereceiving a user-plane data. These may be referred to as dedicatedphysical resource blocks for the reduced-capability terminal device.Also schematically represented in the PDSCH region of each subframe isan indication of the transmission resources 568 the base station woulduse if it were transmitting system information blocks in the relevantsubframe. These may be referred to as SIB physical resource blocks. Itwill be appreciated the respective sets of transmission resources 566,568 are shown as contiguous blocks occurring at the same place in eachsubframe purely for ease of representation. In practice the resources566 comprising the dedicated PRBs for the reduced-capability terminaldevice may not be contiguous and their position and frequency may changein different subframes. Likewise for the resources 566 comprising theSIB PRBs (i.e. they may in general be scheduled on different frequencyresources in each subframe).

In subframes SFn and SFn+1 the reduced-capability terminal device isassumed to be operating in a known “T-shaped” virtual carrier mode ofoperation in which it buffers the full PDCCH region 560 and therestricted subset of PDSCH transmission resources 566 established fordedicated user-plane data transmissions for the reduced-capabilityterminal device. While the device is buffering the dedicated PRBs 566 itis unable to buffer the transmission resources 568 used by the networkfor transmitting system information. This is schematically representedin FIG. 5 by a tick mark in the PDSCH transmission resources 566comprising the dedicated PRBs and a cross mark and shading in the PDSCHresources 568 comprising the SIB PRBs.

In the schematic example represented in FIG. 5 it is assumed the basestation is to make a change to system information at the systeminformation modification period boundary 564 between subframes SFn+1 andSFn+2. The reason for the system information change in any givenimplementation is not significant to the operation of embodiments of thedisclosure.

A reduced-capability terminal device can receive a system informationchange notification from a base station in the same way as for aconventional terminal device in the conventional manner discussed above.Established techniques can also be used to inform the terminal device ofthe transmission resources used for transmitting system information(i.e. the resources 568 identified in FIG. 5 as SIB PRBs).

However, an issue arises in that the reduced-capability terminal devicemay not be able to receive some of the larger SIBs. Further, in order toextend the coverage of these reduced capability devices, repetition ofdata in the SIB may be performed.

The inventors have identified various mechanisms to receive some of thelarger SIBs in reduced capability terminal devices. One approach is tosend a version of the SIB for non reduced-capability terminal devicesand a copy of the SIB specifically for terminal devices operating at 1.4MHz bandwidth and/or with coverage enhancement. This may involveremoving non-essential information and cutting larger blocks down.However, even with this approach, the inventors have identified severalissues.

Firstly, there is not a large amount of information that can beconsidered as not essential. This is particularly true if the lowcomplexity devices need to support inter-frequency mobility. Thisfeature is important in the field of wearable technology (such assmartwatches) as the largest sized SIBs are mobility related. Secondly,it is considered by the inventors to be inefficient to broadcast thesame information twice.

According to the present disclosure, the scheduling information for ablock of system information, such as a SIB, is provided bySchedulingInfoList. This is transmitted to the terminal devices inso-called “SIB1”. A diagram showing the structure of SIB1 according tothe present disclosure is shown in FIG. 6. As with a known SIB1, theSIB1 according to present disclosure is transmitted to the terminaldevices at a fixed time location. In examples, theSystemInformationBlockType1 uses a fixed schedule with a periodicity of80 ms and repetitions made within 80 ms. The first transmission ofSystemInformationBlockType1 is scheduled in subframe #5 of radio framesfor which the SFN mod 8=0, and repetitions are scheduled in subframe #5of all other radio frames for which SFN mod 2=0. Of course, anyappropriate time location may be used

The SchedulingInfoList of the SIB1 structure according to the presentdisclosure contains the scheduling information for the other SIBs. Forexample, SIB2 is used to send common channel (e.g. PCCH and PRACH)configuration. SIB3 is used to send cell re-selection configurationinformation. This is common to inter/intra-freq and inter-RAT (forexample serving cell thresholds and suitability criteria). SIB4 containsinformation specific to intra-frequency reselection. SIB5 containsinformation specific to inter-frequency reselection. SIB6 and SIB7contains UTRAN and GERAN cell reselection information, respectively.This is similar to the known SIB structure. The order of the SIB1structure is defined in the 3GPP TS 36.331 section 6.2.2(SystemInformationBlockType1 Message) Standard.

The SIB1 structure according to embodiments of the present disclosure,however, also includes a flag which indicates whether additionalscheduling information in the form of a SIB designed for reducedcapability terminal devices is included in SIB1. This flag, or adifferent flag, may also indicate whether additional schedulinginformation in the form of a SIB designed for coverage enhancement isincluded in SIB1. In FIG. 6, this additional SIB is identified as “SIBx”and the flag is “SIBx present=true”. Of course, SIBx may relate to theSIB for reduced capability terminal devices and/or coverage enhancementterminal devices. As would be appreciated, although an explicit flag isshown in FIG. 6, in other examples, any marker (a flag or otherwise)indicating that an additional SIB is included may be located in thescheduling information with SIB1, for example, at n=5 in the numberingof FIG. 6 or may be separately included in an existing or newly definedmaster information block (MIB) to indicate the presence of theadditional scheduling block. The marker and the newly defined schedulingmay alternatively also be contained in a newly defined MIB which isseparate to the existing MIB. In other words, the marker indicating thepresence of SIBx is sent in the master information block (MIB) ratherthan SIB1. The terminal device then does not receive (or otherwiseignores) the scheduling information from SIB1 and instead reads only thescheduling information from SIBx.

Of course, and will be explained later, although only a singleadditional SIB is identified by the flag, other embodiments may includemore than one additional SIB specific for reduced capability terminaldevices. For example, one additional SIB may be provided for reducedbandwidth terminal devices and a second additional SIB for coverageenhancement terminal devices. Other embodiments may include an extensionto SIB1 containing the additional scheduling information instead of, orin addition to, an additional one or more SIBs.

So, when a terminal device receives the SIB1 structure according toembodiments of the present disclosure, the terminal device checks forthe presence of the additional SIBx identified by the flag or otherwise.If the terminal device is a reduced capability terminal device, oroperating in coverage enhancement mode, the terminal device willretrieve the SIBx appropriate for the type of reduced capabilityterminal device or the current coverage mode. However, if the terminaldevice is not a reduced capability terminal device, or operating incoverage enhancement mode, the terminal device will ignore theadditional SIB and continue to process the SIB as already known. Thismeans that the SIB1 according to embodiments of the present disclosureis compatible with both non capability reduced terminal devices, devicesoperating in coverage enhancement mode, and legacy devices.

If the terminal device is a capability-reduced terminal device or isoperating in coverage enhancement mode and has identified theappropriate additional SIBx, the terminal device obtains theSchedulingInfoList from SIBx. For the sake of clarity, theSchedulingInfoList of the additional SIBx is termed“SchedulingInfoList_MTC”, although any title may be appropriate.

As will be noted, SchedulingInfoList_MTC contains entries n=1 to n=4which map to entries n=1 to n=4 of SIB1. So, the order of the schedulinginformation for SIB1 is the same as the order of the scheduling for SIBxwhere this mapping occurs. SchedulingInfoList_MTC also contains entriesn=5 to n=7 which do not map to entries within SIB1. The purpose of SIBxis to provide instructions on whether and how the various entries ofSIB1 (for example in FIG. 6, n=1 to n=4) should be altered by thecapability reduced terminal device. The content and function of each ofthese entries within SIBx will now be explained with reference to theSIBx structure located on the right hand side of FIG. 6.

Entry n=1 of SIBx contains the term “Remove(sibType2)”. This means thatthe reduced capability terminal device is instructed to remove SIB2 fromthe entry n=1 within SIB1 and hence no system information block will bereceived at n=1. Entry n=2 of SIBx contains the term “Replace (sibType3)with (sibType3 -defaultConfig1) Remove (sibType4)”. This means that thereduced capability terminal device will replace the sibType3 in entryn=2 of SIB1 and replace this with a default configuration stored withinthe reduced capability device. This default configuration may bepre-stored in the reduced capability device or may be transferred to thereduced capability device using some mechanism. Further, the reducedcapability terminal device will remove (by not receiving) SIB4 from theentry n=2 within SIB1.

Entry n=3 of SIBx contains the term “Reuse(sibType5)”. This means thatthe reduced capability terminal device is instructed to use the contentof SIBS. This may be done using an explicit indication, or for exampleby omitting (leaving empty) the entry n=3 in the SchedulingInfoList_MTC.Entry n=4 of SIBx contains the term “Remove(sibType6, sibType7)”. Thismeans that the reduced capability terminal device will remove (i.e. notreceive) SIB6 and SIB7 from entry n=4 within SIB1 and not attempt toreceive those.

Entry n=5 to n=7 of SIBx do not map to SIB1. Within entry n=5 to n=7,scheduling for the replacement SIBs that have been removed from entryn=1 to n=4 or for any new (additional) SIBs is included. Specifically,in the example of FIG. 6, entry n=5 of SIBx states that SIB4 will besent with a periodicity of 32 radio frames. In other words, comparedwith entry n=2 of SIB1, SIB4 in SIBx is sent on its own without beingcombined with SIB3. By sending a replacement for any of the mobilityrelated system information (e.g. SIB4, SIB5) it is possible to reducethe number of signalled neighbours compared to the SIB scheduled forother devices resulting in a smaller size of system information block.

Entry n=6 and n=7 of SIBx states that SIB2 be effectively split into twoparts, segment 1 and segment 2 (seg1 and seg2 of FIG. 6). Each of thesesegments will have a periodicity of 32 radio frames.

This splitting of a SIB (in this case SIB2) is particularly useful ininstances where a device is located in a weak signal area, such as onthe edge of a cell or in a basement (i.e. operating in a so calledcoverage enhancement mode). Typically, these devices require a SIB to besent many times in order to receive a complete SIB. By splitting the SIBinto segments means that once a segment is received, it does not need tobe re-sent. This saves network resources and battery life within theterminal device.

The use of this additional SIB, SIBx, allows a reduced capabilityterminal device to only use and retrieve SIBs that are relevant to it.This saves battery life within the terminal device. Similarly, in someinstances, it is not possible for the reduced capability terminal deviceto receive the SIB. In this case, the SIB may be split into manysegments and retrieved, or may be simply replaced with a defaultconfiguration.

FIG. 7 shows the relative scheduling of each of the SIBs set out in SIB1and SIBx over time. This is given using the list position and theperiodicity given in SIB1 and SIBx of FIG. 6. As would be appreciated,FIG. 7 is illustrative only; entry n=1 (SIB2) is repeated every 16 radioframes; entry n=2 (SIB3, SIB4) is repeated every 32 radio frames; entryn=3 (SIB5) is repeated every 64 radio frames; entry n=4 (SIB6, SIB7) isrepeated every 128 radio frames; entry n=5 to n=7 is repeated every 32radio frames.

An example will now be given with three different types of terminaldevice and how each may use the information provided in the SIBs todetermine what information to decode. The first is a smartphone, thesecond is a smartwatch and the third is a power meter in a basement.Each of these terminal devices have different capabilities andrequirements.

Let us assume that the smartphone supports LTE category 1, UMTS and GSM.Let us also assume the smartwatch is a narrowband LTE device (Rel-13category) which does not support UMTS or GSM but has to support mobilitywith LTE. Let us finally assume that the smart meter is either acategory 0 (Rel-12) or narrowband (Rel-13) device which also supportscoverage enhancement to receive LTE data, including system information.The smart meter is a stationary device and so does not need to supportmobility.

A legacy terminal device will only receive the SIBs at n=1, 2, 3, 4.This is because the legacy terminal device does not have a restrictionon either RF bandwidth or coverage and so no segmented or reducedinformation is required.

The smartwatch device has narrowband RF so must follow the informationgiven in SIBx. The SIBs received at the smartwatch are shown in FIG. 8.

As the smartwatch is narrowband RF, it is likely that SIB2 (in n=1) willbe too large and is spread over more than 6 physical resource blocks,and it is also likely that SIB2 will be too large to segment to supportrepetition for coverage enhancement, but will be segmented to bereceived by the smartwatch. Therefore, SIB2 in n=1 will not be receivedby either the smartwatch or the smart meter, but will instead bereceived in two segments and provided in n=6 and n=7. By providing thesesegments in n=6 and n=7, they will not be received by the smartphone orlegacy devices. This is because these devices only recognise n=1 to n=4.

The inclusion of SIB3 and SIB4 in n=2 means that SIB3 and SIB4 are alsotoo large to be received by either the smartwatch or the smart meter.SIB5 on the other hand is not too large for 6 physical resource blocksso can be received by the smartwatch. However, as SIB5 relates tointer-frequency reselection parameters, which is a feature of mobility,this is not required by the smart meter and not required to be sentusing repetition for coverage enhancement mode. Therefore, SIB5 onlyneeds to be received by the smartwatch.

SIB6 and SIB7 in n=4 are also too large to be spread over 6 physicalresource blocks and so cannot be received by either the smartwatch orthe smart meter. In any event, as SIB6 and SIB7 relate to UTRAN andGERAN cell reselection respectively, neither the smartwatch nor thesmart meter need this information as they only support LTE. Therefore,SIB6 and SIB7 will not be received by either the smartwatch or the smartmeter (see n=4 in the SIBx where SIB6 and SIB7 are “removed”).

Turning now specifically to FIG. 8 which shows the SIBs received by thesmartwatch. As indicated by SIBx, at n=1, SIB2 is not received as it issegmented into two sections and is provided at n=6 and n=7 instead.

At n=2, the smartwatch does not receive SIB3 or SIB4. Instead, n=2 tellsthe smartwatch to replace the content of SIB3 with a defaultconfiguration which may be a pre-defined common channel configuration;this pre-defined common configuration may either be defined in thespecifications, defined in the SIM function of the smartwatch, or may bepre-established using, for example, dedicated signalling or hard-codedat manufacture according to an operator-specific configuration. This maycontain, for example, fixed reduced capability terminal device specificPRACH resources. Additionally, at n=2 within SIBx, SIB4 is read when itis sent alone in n=5. As SIB4 is not combined with SIB3, SIB4 can besent using less than 6 physical resource blocks. It should be noted herethat the contents of SIB4 (when sent in n=5) may be different to SIB4sent at n=2. This is because the legacy device (such as the smartphone)will not receive n=5 and may require a larger inter-frequency list thanthat of the smartwatch. Therefore, by knowing that n=5 will only bereceived by the smartwatch, it is possible to tailor the SIB informationfor the smartwatch. This reduces network resource and extends batterylife of the smartwatch. It also provides a possibility to performrepetitions in order to support some level of coverage enhancement,which may be required by a reduced capability device in order to meetsimilar performance requirements as a device without reduced capability.This could be, for example, a coverage enhancement of 3 dB to compensatefor the device having only 1 receive antenna.

At n=3, SIB5 from the SchedulingInfoList of SIB1 is reused. This isbecause it is required by the smartwatch and will also fit within 6physical resource blocks.

It is possible to send SIB5 with additional repetitions. This supportsthe use of the smartwatch also requiring repetition. In this case, SIB5would still be scheduled at the same position, but with some additionalrepetitions. As n=3 is received by legacy devices, the provision ofrepetitions of SIB5 means that there is possible further support forcoverage enhancement of legacy devices.

Additionally, with regard to the smart meter, SIB5 is not required asmobility information is not used by the stationary smart meter.Therefore, the smart meter would only need to read the informationcontained in SIBx at n=5, 6 and 7. This has the advantage that, in orderto support coverage extension, only the new SIBs need to be sent withadditional repetitions, while the existing SIBs remain unaffected andrequire no repetitions.

Although the foregoing has indicated that SIBx may include instructionsthat relate to scheduling information of SIBs referenced in SIB1, thepresent disclosure is not so limited. Specifically, SIBx may includeinstructions that tell the terminal device to ignore all schedulinginformation located in SIB1. The scheduling information in SIBx may theninstead provide scheduling information to the terminal device whichrelates to the delivery of newly defined SIB types (i.e. SIB types notlocated in SIB1). In other words, although it is possible that thescheduling information in SIBx relates to the scheduling of SIBsmentioned in SIB1, the present disclosure is not so limited and thescheduling information in SIBx may relate to the scheduling of SIBs notmentioned in SIB1.

Coverage Enhancement

As noted above, SIBx may provide scheduling information for a terminaldevice (either reduced capability or not) operating in coverageenhancement mode. In order to operate in coverage enhancement mode, theSIB will need transmitting with a certain number of repetitionsdepending on the amount of coverage enhancement required by the terminaldevice. For example, a smart watch which may require 3 dB of coverageenhancement will need a SIB repeated less times than a smart meter thatmay require 15 dB of coverage enhancement.

Given this, it is envisaged that a cell may provide more than one levelof coverage enhancement. Specifically, a cell may support normalcoverage (i.e. no coverage enhancement and no repetitions of the SIB); 3dB coverage enhancement which requires some repetitions of the SIB; and15 dB coverage enhancement which requires more repetitions than the 3 dBcoverage enhancement as would be appreciated.

However, the inventors have identified at least one problem with this.In order to support both 3 dB and 15 dB coverage enhancement, the SIBsused by the smartwatch (for 3 dB coverage enhancement) and the SIBs usedby the smart meter (for 15 dB coverage enhancement) are separate andsent with different numbers of repetitions. The smart watch wouldtherefore read the 3 dB coverage enhancement SIB and potentially alsothe 15 dB coverage enhancement SIBs and the smart meter would read onlythe 15 dB coverage enhancement SIB. In other words, the smart watch canread both the 3 dB coverage enhancement SIBs and the 15 dB coverageenhancements SIBs whereas the smart meter would read only the 15 dBcoverage enhancement SIB. So, the terminal device will read the SIBsbased on the capability of the terminal device.

However, the inventors recognise that reading SIBs with a high number ofrepetitions (or any number of repetitions) consumes more energy thanreading a SIB only once. Additionally, some SIBs may only be able to beread in 3 dB coverage enhancement mode due to the size of the block.Further, some networks provide some SIBs (for example SIB4 and SIB5which relate to mobility) only in 3 dB coverage enhancement mode.Therefore, the inventors recognise that a terminal device operating incoverage enhancement mode will prefer to operate in either a lower levelcoverage enhancement mode or no coverage enhancement mode if possible.In other words, in the case above, a terminal device supporting 15 dBcoverage enhancement such as a smart meter, would prefer to eitheroperate in 3 dB coverage enhancement mode or with no coverageenhancement mode. This saves energy and would be supported by morenetworks and could enable additional behaviour such as mobility support.Some terminal devices may prefer to use mobility when in a situationthat only a small level of coverage enhancement is needed, but prefer touse 15 dB coverage enhancement with no mobility rather than being out ofcoverage altogether

FIG. 9 shows a flow chart 900 explaining the process by which a terminaldevice will operate in the most appropriate coverage enhancement mode(or even no coverage enhancement mode).

The process starts in step 902. The terminal device receives the initialsystem information in 904. The system information may include a MIB andSIB and/or SIBx as appropriate. The network will provide the initialsystem information such that can be received by all terminal devices inthe cell. This means that the network will provide system informationthat can be read by terminal devices operating with a maximum level ofcoverage enhancement.

Within the initial system information, one or more thresholds areprovided. These threshold values define the minimum power (for eachlevel of coverage enhancement) at which the cell is considered suitable.This threshold information is similar to that defined currently as theQrxlevmin which is currently provided in SIB1 for example. Of course,this is only an example and any kind of threshold identifying theminimum power at which the cell is considered suitable for each level ofcoverage enhancement is envisaged. The initial system information mayonly reference the location of further system information, with thethresholds being fixed, for example in the terminal device or in thestandards specification.

In this specific case, SIB1 will initially provide the threshold valuefor normal coverage. In other words, SIB1 will include the thresholdvalue for no coverage enhancement. Within SIB1, the remaining thresholdlevels for each of the supported coverage enhancement modes may also beprovided. However, these values may be discrete threshold values or maybe values relative to the no coverage enhancement threshold value (forexample, threshold value for 3 dB coverage enhancement=threshold for nocoverage enhancement−3 dB).

The terminal device retrieves the threshold values in step 906.

The terminal device then compares the measured signal strength (RSRP)against the threshold value for no coverage enhancement in step 908.

The terminal device determines whether the measured signal strength islower than the threshold value for no coverage enhancement in step 910.If the result of the comparison is that the measured signal strength islower, then the “yes” branch is followed. Otherwise, the “no” branch isfollowed. In the event that the “yes” branch is followed, the terminaldevice compares the measured signal strength against the threshold valuefor the first level of coverage enhancement. In this case, the terminaldevice compared the measured signal strength against the threshold valuefor the 3 dB level of coverage enhancement. This is step 912.

If the terminal device determines in step 914 that the measured signalstrength is lower than the threshold value for the 3 dB level ofcoverage enhancement, the “yes” branch is followed. Otherwise, the “no”branch is followed.

In the event that the “yes” branch is followed, the next (in this casesecond) level of coverage enhancement will be tested. Specifically, instep 916, the next level of coverage enhancement is selected. Theprocess repeats steps 912 and 916. In other words, the terminal devicecompares the measured signal strength against the threshold for thesecond level of coverage enhancement (for example 15 dB). This repeatsuntil the measured signal strength is not less than the threshold valueand then an appropriate level of coverage enhancement for that terminaldevice, and that is supported by the network, is selected. The no branchat step 914 is then followed.

When the “no” branch is followed from step 914, the process moves tostep 920. The terminal device knows which level of coverage enhancementto use and therefore which SIB to retrieve. The selection of theappropriate level is performed in step 920 and the reading and retrievalof the appropriate SIB is performed in step 924. The reader is referredto FIGS. 6-8 regarding information explaining the selection of the SIB.

Referring back now to step 910, if the terminal device determines thatthe measured signal strength is not lower than the threshold for nocoverage enhancement, the “no” branch is followed. This means that theterminal device will not operate using coverage enhancement and so willavoid receiving repeated SIBs thus saving energy.

The terminal device will select no coverage enhancement in step 918 andwill read the SIB that is associated with no coverage enhancement instep 922. This SIB may be a modified SIB as explained above in FIGS. 6-8if only certain features are required or may be an unmodified SIB.

Once the terminal device has read the appropriate SIB, the terminaldevice informs the network of the coverage enhancement mode upon whichthe terminal device operates. This may be sent using the PRACH as theterminal device requests certain resources from the network. Of course,other mechanisms for letting the network know such as a specificinstruction sent over the air or otherwise is envisaged. This isperformed in step 926. The process ends in step 928.

This process has a number of advantages. The terminal device can selectthe best level of coverage enhancement based on the terminal devicecapability and the support in the cell. By doing this energy consumptionin the terminal device is achieved.

At the end of the process outlined in FIG. 9, the terminal deviceoperates in a particular coverage enhancement mode. This process may berepeated periodically to ensure that the terminal device operates in themost appropriate coverage enhancement mode.

However, in the event that the measured signal strength changes beforethe process is repeated due to mobility of the terminal device, or dueto the dynamic radio conditions or even due to an incorrectly identifiedmeasured signal strength, the terminal device may not be able to receivethe appropriate SIB. In this case, the terminal device willautomatically operate in the next level of coverage enhancement and willnotify the network appropriately.

For example, if the terminal device operates in the 3 dB coverageenhancement mode and then suddenly the dynamic radio conditions worsento the extent that the 3 dB coverage enhancement SIB can no longer bereceived, the terminal device will begin operating in the 15 dB coverageenhancement mode (instead of the 3 dB coverage enhancement mode) andwill receive the 15 dB coverage enhancement SIB transmitted at theincreased repetition rate. The terminal device will notify the networkof the change of operation mode as noted previously in FIG. 9. It isalso envisaged that failure to receive the system information mayinitiate repeating the process described in FIG. 9.

Although the above describes the threshold values being provided by thenetwork, it is envisaged that the threshold values may be provided tothe terminal device by any appropriate mechanism, such as at manufacture(if the threshold values are set in a Standard) or over WiFi or by anyappropriate means. Indeed the terminal device may receive an index to atable in which the threshold values are stored. This potentially meansless data is transmitted if the index value is smaller than thethreshold value.

FIG. 10 schematically shows a telecommunications system 600 according toan embodiment of the present disclosure. The telecommunications system600 in this example is based broadly around an LTE-type architecturewhich supports virtual carrier operations such as discussed above. Manyaspects of the operation of the telecommunications system 600 are knownand understood and are not described here in detail in the interest ofbrevity. Operational aspects of the telecommunications system 600 whichare not specifically described herein may be implemented in accordancewith any known techniques, for example according to the currentLTE-standards with modifications as appropriate to incorporate virtualcarrier operation, such as disclosed in GB 2 487 906 [2], GB 2 487 908[3], GB 2 487 780 [4], GB 2 488 613 [5], GB 2 487 757 [6], GB 2 487 909[7], GB 2 487 907 [8], GB 2 487 782 [9], GB 2 497 743 [10] and GB 2 497742 [11], the entire contents of which are incorporated herein byreference.

The telecommunications system 600 comprises a core network part (evolvedpacket core) 602 coupled to a radio network part. The radio network partcomprises a base station (evolved-nodeB) 604 coupled to a plurality ofterminal devices. In this example, two terminal devices are shown,namely a first terminal device 606 and a second terminal device 608. Itwill of course be appreciated that in practice the radio network partmay comprise a plurality of base stations serving a larger number ofterminal devices across various communication cells. However, only asingle base station and two terminal devices are shown in FIG. 9 in theinterests of simplicity.

As with a conventional mobile radio network, the terminal devices 606,608 are arranged to communicate data to and from the base station(transceiver station) 604. The base station is in turn communicativelyconnected to a serving gateway, S-GW, (not shown) in the core networkpart which is arranged to perform routing and management of mobilecommunications services to the terminal devices in thetelecommunications system 600 via the base station 604. In order tomaintain mobility management and connectivity, the core network part 602also includes a mobility management entity (not shown) which manages theenhanced packet service, EPS, connections with the terminal devices 606,608 operating in the communications system based on subscriberinformation stored in a home subscriber server, HSS. Other networkcomponents in the core network (also not shown for simplicity) include apolicy charging and resource function, PCRF, and a packet data networkgateway, PDN-GW, which provides a connection from the core network part602 to an external packet data network, for example the Internet. Asnoted above, the operation of the various elements of the communicationssystem 600 shown in FIG. 10 may be broadly conventional, for example inaccordance with established telecoms standards and the principles setout in the referenced documents mentioned herein, apart from wheremodified to provide functionality in accordance with embodiments of thepresent disclosure as discussed herein.

In this example, it is assumed the first terminal device 606 is aconventional smartphone type terminal device communicating with the basestation 604 in a conventional manner. This conventional terminal device606 comprises a transceiver unit 606 a for transmission and reception ofwireless signals and a processor unit (controller unit) 606 b configuredto control the device 606. The processor unit 606 b may comprise aprocessor unit which is suitably configured/programmed to provide thedesired functionality using conventional programming/configurationtechniques for equipment in wireless telecommunications systems. Thetransceiver unit 606 a and the processor unit 606 b are schematicallyshown in FIG. 10 as separate elements. However, it will be appreciatedthat the functionality of these units can be provided in variousdifferent ways, for example using a single suitably programmed generalpurpose computer, or suitably configured application-specific integratedcircuit(s)/circuitry. As will be appreciated the conventional terminaldevice 606 will in general comprise various other elements associatedwith its operating functionality.

In this example, it is assumed the second terminal device 608 is amachine-type communication (MTC) terminal device 604 adapted to operatein a virtual carrier (VC) mode in accordance with embodiments of thepresent disclosure when communicating with the base station 604. Asdiscussed above, machine-type communication terminal devices can in somecases be typically characterised as semi-autonomous or autonomouswireless communication devices communicating small amounts of data.Examples include so-called smart meters which, for example, may belocated in a customer's house and periodically transmit information backto a central MTC server data relating to the customer's consumption of autility such as gas, water, electricity and so on. MTC devices may insome respects be seen as devices which can be supported by relativelylow bandwidth communication channels having relatively low quality ofservice (QoS), for example in terms of latency. It is assumed here theMTC terminal device 608 in FIG. 9 is such a device.

The MTC device 608 comprises a transceiver unit 608 a for transmissionand reception of wireless signals and a processor unit (controller unit)608 b configured to control the MTC device 608. The processor unit 608 bmay comprise various sub-units for providing functionality in accordancewith some embodiments of the present disclosure as explained furtherherein. These sub-units may be implemented as discrete hardware elementsor as appropriately configured functions of the processor unit. Thus theprocessor unit 608 b may comprise a processor which is suitablyconfigured/programmed to provide the desired functionality describedherein using conventional programming/configuration techniques forequipment in wireless telecommunications systems. The transceiver unit608 a and the processor unit 608 b are schematically shown in FIG. 10 asseparate elements for ease of representation. However, it will beappreciated that the functionality of these units can be provided invarious different ways, for example using a single suitably programmedgeneral purpose computer, or suitably configured application-specificintegrated circuit(s)/circuitry, or using a plurality of discretecircuitry/processing elements for providing different elements of thedesired functionality. It will be appreciated the MTC device 608 will ingeneral comprise various other elements associated with its operatingfunctionality in accordance with established wireless telecommunicationstechniques.

The base station 604 comprises a transceiver unit 604 a for transmissionand reception of wireless signals and a processor unit (controller unit)604 b configured to control the base station 604 to operate inaccordance with embodiments of the present disclosure as describedherein. The processor unit 606 b may again comprise various sub-unitsfor providing functionality in accordance with embodiments of thepresent disclosure as explained further below. These sub-units may beimplemented as discrete hardware elements or as appropriately configuredfunctions of the processor unit. Thus, the processor unit 604 b maycomprise a processor which is suitably configured/programmed to providethe desired functionality described herein using conventionalprogramming/configuration techniques for equipment in wirelesstelecommunications systems. The transceiver unit 604 a and the processorunit 604 b are schematically shown in FIG. 10 as separate elements forease of representation. However, it will be appreciated that thefunctionality of these units can be provided in various different ways,for example using a single suitably programmed general purpose computer,or suitably configured application-specific integratedcircuit(s)/circuitry or using a plurality of discretecircuitry/processing elements for providing different elements of thedesired functionality. It will be appreciated the base station 604 willin general comprise various other elements associated with its operatingfunctionality in accordance with established wireless telecommunicationstechniques.

Thus, the base station 604 is configured to communicate data with boththe conventional terminal device 606 and the terminal device 608according to an embodiment of the disclosure over respectivecommunication links 610, 612. The communication link 610 forcommunications between the base station 604 and the conventionalterminal device 606 is supported by a host carrier (e.g. potentiallymaking use of the full range of transmission resources schematicallyrepresented in FIG. 4). The communication link 612 for communicationsbetween the base station 604 and the reduced-capability MTC terminaldevice 608 is supported by a virtual carrier (e.g. making use ofresources within a restricted subset of frequency resources such as thevirtual carrier schematically represented in FIG. 4). Communicationsbetween the MTC terminal device 608 and the base station 604 maygenerally be based on any of the previously proposed schemes for virtualcarrier operation with modification as described herein to providefunctionality in accordance with certain embodiments of the disclosure.For example, the MTC terminal device 608 may operate such that allcontrol-plane and user-plane signalling from the base station 604 whichis addressed to the terminal device 608 is made within the subset offrequency resources (OFDM carriers) allocated to the virtual carrierprovided for the terminal device 608. Alternatively, control-planesignalling from the base station 604 which is addressed to the terminaldevice 608 may be made within the full-bandwidth of the control region300 represented in FIG. 4, with higher-layer data (user-plane data)being communicated within the restricted frequency resources (OFDMcarriers) allocated to the virtual carrier provided for the terminaldevice 608.

Finally, although the foregoing has described the terminal device as asmart watch as a wearable device, any type of wearable device isenvisaged. For example, according to present principles, the wearabledevice may be smart glasses, or a fitness band. Further, the device maybe located in a vehicle such as a car or van or a boat.

Embodiments of the present disclosure can be exemplified by thefollowing numbered paragraphs.

-   1. A method of operating a terminal device capable of coverage    enhancement in a wireless telecommunication system comprising    receiving a signal from a base station within the wireless    telecommunication system, measuring the received signal strength of    the received signal, comparing the measured signal strength with at    least one threshold value and selecting the mode of operation of    coverage enhancement based on the result of the comparison.-   2. A method according to paragraph 1, wherein the received signal    comprises system information which indicates the threshold value.-   3. A method according to paragraph 1 or 2, wherein the at least one    threshold value relates to the minimum level of power supported by    the base station at a particular level of coverage enhancement.-   4. A method according to paragraph 1, 2, or 3 comprising receiving    system information associated with the selected mode of operation of    coverage enhancement.-   5. A method according to any preceding paragraph, comprising    transmitting to the wireless telecommunication system the selected    mode of coverage enhancement.-   6. A method according to paragraph 5, wherein the selected mode is    transmitted in the physical random access channel.-   7. A method according to any preceding paragraph, wherein when    operating in the selected mode of operation, in the event that the    system information associated with the selected mode of operation is    not received, the method comprises: selecting a different mode of    coverage enhancement.-   8. A terminal device capable of coverage enhancement for use in a    wireless telecommunication system wherein the terminal device    comprises a transceiver unit and a control unit, wherein the control    unit is configured to control the transceiver unit to receive a    signal from a base station within the wireless telecommunication    system, and to measure the received signal strength of the received    signal, and the control unit is further operable to compare the    measured signal strength with at least one threshold value and    select the mode of operation of coverage enhancement based on the    result of the comparison.-   9. A terminal device according to paragraph 8, wherein the received    signal comprises system information which indicates the threshold    value.-   10. A terminal device according to paragraph 8 or 9, wherein the at    least one threshold value relates to the minimum level of power    supported by the base station at a particular level of coverage    enhancement.-   11. A terminal device according to paragraph 8, 9 or 10, wherein the    control unit is configured to control the transceiver unit to    receive system information associated with the selected mode of    operation of coverage enhancement.-   12. A terminal device according to any preceding paragraph, wherein    the control unit is configured to control the transceiver unit to    transmit to the wireless telecommunication system the selected mode    of coverage enhancement.-   13. A terminal device according to paragraph 12, wherein the    selected mode is transmitted in the physical random access channel.-   14. A terminal device according to any preceding paragraph, wherein    when operating in the selected mode of operation, in the event that    the system information associated with the selected mode of    operation is not received, the wherein the control unit is    configured to select a different mode of coverage enhancement.-   15. A base station for use in a wireless telecommunication system    comprising a transceiver unit and a control unit, the control unit    being configured to control the transceiver unit to transmit to a    terminal device according to any one of paragraphs 8 to 14 a    plurality of different system information blocks, each system    information block being associated with a different mode of coverage    enhancement.-   16. A wireless telecommunication system comprising a base station    according to paragraph 15 and a terminal device.

REFERENCES

[1] ETSI TS 122 368 V11.6.0 (2012 September)/3GPP TS 22.368 version11.6.0 Release 11)

[2] GB 2 487 906 (UK patent application GB 1101970.0)

[3] GB 2 487 908 (UK patent application GB 1101981.7)

[4] GB 2 487 780 (UK patent application GB 1101966.8)

[5] GB 2 488 513 (UK patent application GB 1101983.3)

[6] GB 2 487 757 (UK patent application GB 1101853.8)

[7] GB 2 487 909 (UK patent application GB 1101982.5)

[8] GB 2 487 907 (UK patent application GB 1101980.9)

[9] GB 2 487 782 (UK patent application GB 1101972.6)

[10] GB 2 497 743 (UK patent application GB 1121767.6)

[11] GB 2 497 742 (UK patent application GB 1121766.8)

[12] Holma H. and Toskala A, “LTE for UMTS OFDMA and SC-FDMA based radioaccess”, John Wiley and Sons, 2009

[13] ETSI TS 136 331 V11.4.0 (2012 July)/3GPP TS 36.331 version 11.4.0Release 11

1. A terminal device capable of coverage enhancement for use in awireless telecommunication system wherein the terminal device comprises:circuitry configured to receive master information block (MIB) includinginformation indicating the presence of scheduling information for firstsystem information block (SIB), the MIB being broadcast by a basestation; receive the first SIB including at least a first threshold anda second threshold, the system information being broadcast by the basestation, the first threshold indicating minimum power level for a firstmode without coverage enhancement and the second threshold indicatingminimum power level for a second mode with coverage enhancement; performa measurement to obtain a signal strength from the base station;selecting the first mode as a selected mode of coverage enhancement whenthe measured signal strength is greater than the first threshold value;not selecting the first mode as the selected mode of coverageenhancement and comparing the measured signal strength with a secondthreshold value when the measured signal strength is less than the firstthreshold value; selecting the second mode as the selected mode ofcoverage enhancement when the measured signal strength is greater thanthe second threshold value; and perform random access procedures withselected physical random access channel (PRACH) resources, the selectedPRACH resources being associated with the selected mode of coverageenhancement.
 2. The terminal device according to claim 1, wherein systeminformation procedures between the base station and the terminal devicein the second mode are identical to system information procedures for areduced-capability terminal device configured to operate in a subset ofan entirety of a bandwidth of the wireless telecommunication system. 3.The terminal device according to claim 2, wherein in the first mode ofcoverage enhancement transmission of a SIB for the terminal device isrepeated a first number of times, and in the second mode of coverageenhancement transmission of a SIB for the terminal device is repeated asecond number of times, which is greater than the first number of times.4. The terminal device according to claim 3, wherein the SIB is a SIBx aspecifically configured for the reduced-capability terminal device, andexistence of the SIBx is identified by an information element includedin the MIB previously received by the terminal device.
 5. The terminaldevice according to claim 1, wherein the circuitry is configured toreceive system information associated with the selected mode ofoperation of coverage enhancement.
 6. The terminal device according toclaim 1, wherein when operating in the selected mode of operation, inthe event that the system information associated with the selected modeof operation is not received, the circuitry is configured to select adifferent mode of coverage enhancement.
 7. The terminal device accordingto claim 1, wherein the first mode of coverage enhancement is a 3 dBcoverage enhancement mode, and the second mode of coverage enhancementis a 15 dB coverage enhancement mode.
 8. A network device forcommunicating with a terminal device capable of coverage enhancement foruse in a wireless telecommunication system wherein the network devicecomprises: circuitry configured to transmit master information block(MIB) including information indicating the presence of schedulinginformation for first system information block (SIB), the MIB beingbroadcast to devices including the terminal device; transmit the firstSIB including at least a first threshold and a second threshold, thesystem information being broadcast to devices including the terminaldevice, the first threshold indicating minimum power level for a firstmode without coverage enhancement and the second threshold indicatingminimum power level for a second mode with coverage enhancement; andreceive, from the terminal device, random access procedures withselected physical random access channel (PRACH) resources, the selectedPRACH resources being associated with a mode of coverage enhancement,wherein the mode of coverage enhancement is selected as the first modewhen a measured signal strength is greater than the first thresholdvalue, and the mode of coverage enhancement is selected as the secondmode when the measured signal strength is lower than the first thresholdvalue and greater than the second threshold value.
 9. The network deviceaccording to claim 1, wherein system information procedures between thenetwork device and the terminal device in the second mode are identicalto system information procedures for a reduced-capability terminaldevice configured to operate in a subset of an entirety of a bandwidthof the wireless telecommunication system.
 10. The network deviceaccording to claim 9, wherein in the first mode of coverage enhancementtransmission of a SIB for the terminal device is repeated a first numberof times, and in the second mode of coverage enhancement transmission ofa SIB for the terminal device is repeated a second number of times,which is greater than the first number of times.
 11. The network deviceaccording to claim 10, wherein the SIB is a SIBx a specificallyconfigured for the reduced-capability terminal device, and existence ofthe SIBx is identified by an information element included in the MIBpreviously received by the terminal device.
 12. The network deviceaccording to claim 8, wherein the circuitry is configured to transmitsystem information associated with the selected mode of operation ofcoverage enhancement.
 13. The network device according to claim 8,wherein the first mode of coverage enhancement is a 3 dB coverageenhancement mode, and the second mode of coverage enhancement is a 15 dBcoverage enhancement mode.
 14. A method for communicating with aterminal device capable of coverage enhancement for use in a wirelesstelecommunication system wherein the network device comprises:transmitting master information block (MIB) including informationindicating the presence of scheduling information for first systeminformation block (SIB), the MIB being broadcast to devices includingthe terminal device; transmitting the first SIB including at least afirst threshold and a second threshold, the system information beingbroadcast to devices including the terminal device, the first thresholdindicating minimum power level for a first mode without coverageenhancement and the second threshold indicating minimum power level fora second mode with coverage enhancement; and receiving, from theterminal device, random access procedures with selected physical randomaccess channel (PRACH) resources, the selected PRACH resources beingassociated with a mode of coverage enhancement, wherein the mode ofcoverage enhancement is selected as the first mode when a measuredsignal strength is greater than the first threshold value, and the modeof coverage enhancement is selected as the second mode when the measuredsignal strength is lower than the first threshold value and greater thanthe second threshold value.
 15. The method according to claim 14,wherein system information procedures between the network device and theterminal device in the second mode are identical to system informationprocedures for a reduced-capability terminal device configured tooperate in a subset of an entirety of a bandwidth of the wirelesstelecommunication system.
 16. The method according to claim 15, whereinin the first mode of coverage enhancement transmission of a SIB for theterminal device is repeated a first number of times, and in the secondmode of coverage enhancement transmission of a SIB for the terminaldevice is repeated a second number of times, which is greater than thefirst number of times.
 17. The method according to claim 16, wherein theSIB is a SIBx a specifically configured for the reduced-capabilityterminal device, and existence of the SIBx is identified by aninformation element included in the MIB previously received by theterminal device.
 18. The network device according to claim 14, whereinthe circuitry is configured to transmit system information associatedwith the selected mode of operation of coverage enhancement.
 19. Thenetwork device according to claim 14, wherein the first mode of coverageenhancement is a 3 dB coverage enhancement mode, and the second mode ofcoverage enhancement is a 15 dB coverage enhancement mode.